Wide band receiver



May 12, 1942. -w.- R. KOCH WIDE BAND RECEIVER Filed June 1, 1940 9411/0 P3195 4MP! I'FIEIB Patented May 12, 1942 UNITED PATENT] OFFICE WIDE BAND RECEIVER Winfield R. Koch, Haddonfield, N. J., assignor to Radio Corporation of America, a corporation of" Delaware Application June 1, 1940, Serial No. 338,312

6 Glaims. (01. 250-20) sive automatic volume control means, oscillator signal responsive audio frequency volume control means for controlling the signal output level or volume of the receiving system and a combined tuning and volume control oscillator adapted to be remotely located with respect to the main receiving system.

The invention will further be understood from the following description when considered in narrow band receivers, only the oscillator need be tuned. Therefore it may be placed at any suitable remote location near the receiving system and inductively coupled thereto as is well known.

The oscillator coupling in the present system differs from that previously employed for remote signal receiving system having signal responconnection with the accompanying drawing, and

the scope of the said invention is defined in the appended claims.

In the drawing,

Figure 1 is a schematic circuit diagram of a wide-band high frequency radio signal receiving system provided with tuning and volume control means embodying the invention, and

Figure 2 is a schematic circuit diagram of the oscillator control unit for controlling the volume and tuning of the receiving system shown in Fig. 1.

Referring to the drawing, the receiving system is provided with a signal input circuit including a band pass filter 5 coupled to the signal input grid 6 of a first detector 1 to supply thereto signals in one or more predetermined frequency bands, from a signal source suchas an antenna 8. The detector is coupled to an intermediate frequency amplifier 9 followed by a second detector Ii], the output of which is supplied to the signal grid I l of an audio frequency amplifier I2, which in turn is coupled to additional audio amplifier means I3 and a sound output or loudspeaker device I4.,

The receiving system referred to, is representative of any wide band, high frequency, radio receiving system, such for example as a frequency modulation receiver. The system preferably is provided with avc means, comprising, in the present example, a second detector ID for supplying control potentials through an avc circuit l5 to the intermediate frequency amplifier and the first detector grid 6, and being effective to maintain on the signal grid H of the audio frequency amplifier l2 substantially a constant signal potential with signal strength variations.

In wide band frequency modulationreceivers, in radio signal receivers having an intermediate frequency higher than the signal, and in other tuning control in that it also controls the re sponse of a band pass amplifier l8 and an avc circuit l9 therein, together witha control amplifier 20 and the gain of the audio frequency amplifier through the amplifier stage l2, or any other suitable amplifier stage adapted for gain control.

The oscillator is contained in a separate unit I 22 preferably adapted to be portable and, therefore, battery operated, and comprises an oscillator tube 23 having a tunable oscillator circuit 24 provided with a variable tuning element such as a variable capacitor 25 connected with asuitable tuning control element 26 and having an output circuit 2! including an output potentiometer device 28' through which the output circuit is coupled to a small transmitting coil or loop 29, The volume control device is provided with a contact 30 having a control element 3| and theoscillator is energized by a control switch 32 operated by a control element 33.

The oscillator is tunable through a predetermined frequency range to provide the desired high intermediate frequency. in response to signals received through the band pass filter 5, and the strength of the oscillations radiated from the loop or coil 29 iscontrolled by the potentiometer 2830.

The oscillations are picked up on a small receiving loop or coil 35 connected with the band" aband pass interstage coupling transformer 38 between the stage 31 and a second stage 3'9, and a third bandpass coupling transformer 40, coupling the second stage 39 with an oscillator input the presence of signals from the oscillator 23 provides a corresponding negative biasing potential for said grids, thereby-maintaining the oscillator signal input, upon the converter 1 within predetermined limits as the volume control potentiometer 2830 is adjusted at the re- 7 mote unit.

The variable biasing potential derived from the source 52 is also applied to a control grid 55 in the control amplifier stage 20, an increase in the oscillator signal strength being effective to cause the anode current of the stage 20 to be reduced, in the system shown. The anode current flows through a resistor or suitable anode circuit impedance 56 connected in circuit with gain control means in the signal channel following the main a.v.c. controlled portion thereof, such as a control grid 51 in the audio frequency amplifier tube I2. As shown, the bias potential on the grid 51 is varied in a direction to cause the audio frequency gain in the stage l2 to increase with increased oscillator signal strength.

In the present example, the cathode 59 of the stage I2 is returned to an adjustable tap 60 on a potential supply potentiometer resistor 6| substantially three volts more positive than the anode connection 62 for the control amplifier 20.

and a reduction in the audio frequency amplifier gain to a minimum.

As the volume control contact 30 at the remote control point is moved to increase the oscillator output, the gain of the band pass amplifier is reduced to maintain a constant oscillator signal input on the detector 01' converter 1 and at the same time the anode current of the control stage is decreased thereby reducingthe negative bias amplifier having means for receiving and conveying signals from said oscillator to said converter, means for automatically varying the gain of said amplifier in response to variations in the output amplitude of said oscillator including a variable source of biasing potential, a variable gain audio frequency amplifier in the signal channel of said system connected with said source of biasing potential, and means for varying the output amplitude of said oscillator thereby to vary the volume output of said system.

4. In a high frequency signal receiving system, the combination with a signal converter, of a tunable oscillator for varying the tuning of said system through a predetermined frequency range, a band pass amplifier providing coupling means between said oscillator and said converter, gain control means in said amplifier responsive to variations in the signal output of said oscillator for maintaining the signal output from said amplifier substantially constant, gain control means in the signal channel of said receiving system connected with said last named means for increasing the volume level of the signal output of said system on the gain control stage I2 and resulting in a tuning control by remote oscillation supply for heterodyning incoming signals, and remote volume control means for the output of the receiving system.

' I claim as my invention:

1. In a high frequency radio signal receiving system, the combination with a tunable local oscillator, of means for varying the frequency response of the signal receiving circuits of said system in response to variations in the tuning of said oscillator, means for varying the output amplitude of said oscillator, and means for varying the signal volume level in said system in response to variations in the oscillator output amplitude, whereby said oscillator provides combined tuning and volume control means for said system.

2. In a wide band high frequency receiver, the combination with a, tunable local oscillator and aconverter having two input electrodes, of a sigplifier, and means in the first-named channel and connected with said last named means for controlling the signal volume output of said receiver.

3. In a radio signal receiving system, the combination of a signal converter, a tunable local oscillator, a signal channel including a band pass in response to an increase in the output of said oscillator, and means for varying the amplitude of said oscillations whereby said oscillator functions as a combined unitary tuning and volume control means for said system.

5. In a high frequency radio signal receiving system having a signal channel, the combination with a signal converter and a tunable local oscillator, of band pass filter means for applying received signals to said converter, a band pass amplifier responsive to oscillations from said oscillator and including at least one gain controlling amplifier stage, means for coupling said band pass amplifier to said oscillator and to said converter thereby to convey oscillations from said oscillator to said converter, means responsive to variationsin the amplitude of oscillations from said oscillator for varying the gain of said band pass amplifier to provide substantially constant oscillation strength at said converter, an audio frequency amplifier in the signal channel of said system, means for controlling the gain of said audio frequency amplifier in an opposite sense with respect to variations in the gain of the band pass amplifier.

6. In a high frequency radio signal receivin system having a signal channel, the combination with a signal converter and a tunable local oscillator, of band pass filter means for applying received signals to said converter, a band pass amplifier responsive to oscillations from said oscillator and including at least one gain controlling amplifier stage, means for coupling said band pass amplifier to said oscillator and to said converter thereby to convey oscillations from said oscillator to said converter, means responsive to variations in the amplitude of oscillations from said oscillator for varying the gain of said band pass amplifier to provide substantially constant oscillation strength at said converten'an audio frequency amplifier in the signal channel of said system, means for controlling the gain of said audio frequency amplifier in an opposite sense with respect to variations in the gain of the band pass amplifier; and automatic volume control means interposed between said converter and said audio frequency amplifier for maintaining the signal level at said amplifier substantially constant with variations in signal strength.

WINFIELD R. Koorr. 

